Which expression is a perfect cube x^8 y^24 m^28 s^64

Which of the following parabolas opens down?

Square a has a side length of (2x-7) and square b has a side length of (-4x+18). how much bigger is the perimeter of square b than square a?and show all work! you so

The width of a rectangle is half as long as the length. the rectangle has an area of 18 square feet. what are the length and width of the rectangle?